A conventional technology for preventing rotation of a tappet in a supply pump is known (JP 62-090977 U). An exemplar technology for preventing rotation of a tappet in a supply pump is shown in FIG. 7. The supply pump in the exemplar technology includes a cylindrical tappet 106 and an elongated hole 109 provided in a lateral surface of the tappet 106, as shown in FIG. 7. The elongated hole 109 extends in an axial direction of the tappet 106. The supply pump further includes an anti-rotation pin 110 attached to a housing from outside, so that the anti-rotation pin 110 engages with the elongated hole 109 of the tappet 106 to prevent rotation of the tappet 106.
The anti-rotation pin 110 is inserted into an attachment hole provided in the housing to be fixed to the housing. Specifically, the anti-rotation pin 110 has a male screw portion 113 provided on an outer periphery of the anti-rotation pin 110, and the male screw portion 113 is screwed into a female screw portion provided on an inner periphery of the attachment hole of the housing. Accordingly, the anti-rotation pin 110 is fixed to the housing.
In the exemplar technology, when the anti-rotation pin 110 is attached to the housing, the anti-rotation pin 110 may be screwed in a state where positions of the anti-rotation pin 110 and the elongated hole 109 are misaligned. In other words, torque generated by the screwing of the anti-rotation pin 110 may applied on an outer periphery of the tappet 106. As a result, the tappet 106 may be damaged due to the assembling failure.
The anti-rotation pin 110 prevents the rotation of the tappet 106 by contacting the elongated hole 109 of the tappet 106. Thus, the tappet 106 may add a force (impact force) on the anti-rotation pin 110, and the anti-rotation pin 110 may be unfixed from the housing. Because of the unfixing of the anti-rotation pin 110, fuel may leaks from the attachment hole of the housing.
An end portion of the anti-rotation pin 110 contacts the elongated hole 109 of the tappet 106 to prevent the rotation of the tappet 106. Thus, the end portion of the anti-rotation pin 110 is required to be resistant to abrasion. Moreover, an outer side portion of the anti-rotation pin 110 is exposed to atmosphere. Hence, the outer side portion of the anti-rotation pin 110 is required to be resistant to corrosion. Accordingly, what the anti-rotation pin 110 is required is different in between the end portion contacting the tappet 106 and the outer side portion exposed to the atmosphere. Therefore, a heat treatment method and a surface treatment method for the anti-rotation pin 110 may be limited.